What should you know about black kidney stones?

A stone’s surface can look dark because of its mineral content, concentrated urine, blood staining, or changes that occur while it passes. Appearance is not a reliable way to name the composition. Dehydration can make urine more concentrated and may support stone formation, but it does not explain every dark stone. Kidney stones may cause waves of flank or abdominal pain, nausea, blood in the urine, painful urination, or difficulty passing urine. Some remain quiet until they move into the urinary tract.

If you pass a stone, place it in a clean container if you can do so safely and ask how it can be analysed. Arrange a GP consultation to review pain, urine changes, previous stones, fluid intake, medicines, and relevant health conditions. An abdominal ultrasound may help show a stone or blockage, although another test may be needed when the picture is unclear. Drink fluids according to clinical advice; forcing large amounts during severe obstruction can worsen discomfort. Do not rely on colour to choose treatment.

Seek urgent medical help for severe or persistent flank pain, fever or chills, repeated vomiting, inability to pass urine, or painful urination with feeling very unwell. A blocked urinary tract with infection can become serious. Emergency assessment is also appropriate for faintness, confusion, or pain that cannot be controlled. Do not wait for a stone to pass if urine flow stops or infection symptoms appear.

Can the passed stone be analysed? Do I need an abdominal ultrasound? Could dehydration or another condition have contributed? Which pain medicines and fluid plan are suitable? What symptoms mean I should return urgently?